Calendula · Wheaton, Illinois, United States
When to plant calendulas in Wheaton
Main outdoor window
5 Apr - 3 May
A climate estimate. Check your soil, forecast and cultivar.
Timed from last spring frost
26 April
In Wheaton, on your chosen risk.
First flowers
30 May - 14 Jun
If you plant at the start of the window.
The average last frost. Half of all years are later than this.
Step by step in Wheaton
Download these planting dates (.ics)
Import into Apple Calendar, Google Calendar or Outlook. Dates use the selected risk level and are planning estimates, not frost alerts.
Each window is a planning range. Check the forecast, soil and cultivar before planting; a later date is not automatically safer in hot or wet conditions.
Start indoors
15 Mar - 12 Apr
Six weeks before your last frost, under cover or on a windowsill.
Sow direct
5 Apr - 3 May
Three weeks before your last frost.
Plant out
12 Apr - 10 May
Two weeks before your last frost.
In flower
30 May - 14 Jun
Calendulas through the year
Against the frost risk in Wheaton
Seasonal context
Rainfall and the growing season in Wheaton
May has the highest average precipitation (121 mm); January has the lowest (44 mm). Compare this pattern with the planting windows and your water supply.
During wetter months, check that beds and containers drain after heavy rain. During drier months, plan how you will keep seeds and new transplants watered. Monthly averages can hide long dry spells and intense storms; they do not show soil moisture, humidity or this week's weather.
Source: NASA POWER, corrected MERRA-2 precipitation, 2001–2020. Values are approximate monthly totals, including the water equivalent of snow, from the nearest 0.5° × 0.625° grid cell. This reference period differs from the temperature record. Rainfall provides context and does not change the calculated planting dates. Method and limitations.
Monthly growing conditions in Wheaton
Compare the planting window with the local temperature pattern. These are historical monthly averages, not this year's forecast or measured soil temperatures. Average frost days do not tell you whether a particular night will freeze.
| Month | Average low | Average high | Frost days |
|---|---|---|---|
| January | -9.8°C (14.4°F)14.4°F (-9.8°C) | -1.5°C (29.3°F)29.3°F (-1.5°C) | 29.4 |
| February | -8.2°C (17.3°F)17.3°F (-8.2°C) | 1.1°C (33.9°F)33.9°F (1.1°C) | 26.6 |
| March | -2.4°C (27.6°F)27.6°F (-2.4°C) | 7.7°C (45.9°F)45.9°F (7.7°C) | 23.1 |
| April | 2.6°C (36.7°F)36.7°F (2.6°C) | 14.5°C (58.1°F)58.1°F (14.5°C) | 8.7 |
| May | 8.8°C (47.8°F)47.8°F (8.8°C) | 20.7°C (69.3°F)69.3°F (20.7°C) | 0.3 |
| June | 14.7°C (58.5°F)58.5°F (14.7°C) | 26.3°C (79.3°F)79.3°F (26.3°C) | 0.0 |
| July | 17.6°C (63.8°F)63.8°F (17.6°C) | 28.7°C (83.6°F)83.6°F (28.7°C) | 0.0 |
| August | 17.2°C (63°F)63°F (17.2°C) | 28.3°C (83°F)83°F (28.3°C) | 0.0 |
| September | 12.9°C (55.2°F)55.2°F (12.9°C) | 24.7°C (76.4°F)76.4°F (24.7°C) | 0.0 |
| October | 5.9°C (42.7°F)42.7°F (5.9°C) | 17°C (62.6°F)62.6°F (17°C) | 3.2 |
| November | -0.7°C (30.7°F)30.7°F (-0.7°C) | 8.4°C (47.2°F)47.2°F (8.4°C) | 18.0 |
| December | -6.3°C (20.6°F)20.6°F (-6.3°C) | 1.4°C (34.5°F)34.5°F (1.4°C) | 27.5 |
For calendulas, also check drainage, sunlight and cultivar requirements. See the rainfall context above; humidity, irrigation and local pest pressure are not calculated.
Local growing check
Before choosing calendulas for Wheaton
- May is the wettest month in the rainfall grid, averaging about 121 mm. Check how your own bed drains and plan watering around actual soil moisture; monthly rain totals are not an irrigation schedule.
The temperature and rainfall tables on this page show the underlying climate estimates. How these suitability checks work · Record what happens in your garden.
Before you plant calendulas
Use the calendar to plan ahead, then check the conditions in your own garden.
- Measure the soil at sowing depth. Aim for at least 7°C (44.6°F); the calendar estimates soil warmth from air temperatures and cannot measure your bed.
- Frost tolerance does not make saturated or frozen soil suitable for planting. Wait until the bed can be worked without smearing or compacting it.
- Harden off plants raised indoors: gradually expose them to outdoor light, wind and temperature before their final move into the bed.
- Use the maturity range on your seed packet when choosing a variety. Cold, short days and transplant stress can make harvest later than the calendar estimate.
Keep calendula flowering through timely cutting and a suitable season
Use a sunny, drained bed, with some protection from intense heat where needed. Avoid excessive shade, which can make plants leggy. Pinch young growth if a branching plant suits your display.
Remove spent flowers to encourage further buds or reserve selected heads for seed. When heat or disease reduces quality, compare a replacement sowing with trying to revive old plants. If growing petals for food, use correctly identified plants raised for edible use.
What to record this season
Which sowing flowered well before heat or mildew reduced the display? Add the cultivar, sowing date and conditions to your growing record so you can compare next season.
Further reading: NC State Extension: Calendula officinalis . General crop guidance; local dates on this site are calculated separately. Source checked 19 September 2026 by Safe to Plant; this is not an expert review.
The reference describes plant identity and cultivation. Its regional calendar months and hardiness observations do not validate the calculated dates for another location.
How the dates are calculated and their limits · Keep a growing record · Report a local discrepancy
Why these dates
Use a sunny, drained bed, with some protection from intense heat where needed. Avoid excessive shade, which can make plants leggy. Pinch young growth if a branching plant suits your display.
Check the named variety and local forecast before exposing young growth. The catalog cold-damage figure is a reference, not a guarantee: plant age, acclimatisation, wind and the duration of a freeze affect damage.
This calendar uses frost-relative offsets as a starting point. Calendulas are timed from 6 weeks before that frost for an indoor start, with planting out 2 weeks before it, and this page simply resolves those offsets against the frost date computed for Wheaton.
The calendar also applies a soil-warming estimate derived from historical air temperatures. Where that estimate is later than the frost-based date, it delays the window. Soil in your own garden can warm earlier or later; a thermometer at sowing depth is a better final check. Cold, wet conditions can slow germination and increase decay risk.
Wheaton is zone 5b, within the crop's general range. This is an initial cold-hardiness check; cultivar, exposure, drainage and unusual winters can still change the outcome.
The median frost-free season here is 179 days, against 55 to 70 days to first flower for this crop counted from sowing. That margin is what decides whether a late sowing is worth attempting.
Growing calendulas in Wheaton
Can I grow calendulas in Wheaton?
The calendar estimates a planting window, not a guarantee of success. May is the wettest month in the rainfall grid, averaging about 121 mm. Check how your own bed drains and plan watering around actual soil moisture; monthly rain totals are not an irrigation schedule.
When should I plant calendulas in Wheaton?
Aim for 5 Apr - 3 May in an average year. If you would rather not gamble on the weather, wait until 21 Apr - 19 May - by then frost has finished in nine years out of ten.
When might calendulas flower in Wheaton?
The estimated period is 30 May - 14 Jun, based on 55 to 70 days from the modeled planting date. Cultivar, planting material and growing conditions can change this interval; check the plant as well as the calendar.
How much frost will calendulas tolerate?
Check the named variety and local forecast before exposing young growth. The catalog cold-damage figure is a reference, not a guarantee: plant age, acclimatisation, wind and the duration of a freeze affect damage.